Polymers, compositions comprising large organic molecules made from smaller molecules that are linked and cross-linked like chains and nets, are relatively new, having been synthetically produced and commercially developed within the past fifty years. Their many advantages include light weight, moldability, case of forming into intricate configurations, corrosion resistance, versatile electrical properties and low manufacturing cost. These advantages make them suitable for many every day uses such as in our automobiles and kitchens as well as in high-technology industrial and engineering applications. However, inherent softness and tendency to wear away after prolonged use have made polymers impractical materials when hardness and durability are needed.
Attempts have been made to improve the surface characteristics of polymers by use of ion implantation, ion beam irradiation, high performance organic coatings and thin inorganic oxide coatings. Although these treatments have made some polymers more useful, there is a continuing need to develop polymers having hard surfaces that are resistant to wear.
Polymeric materials have been used in spacecraft technology for various applications such as thermal control coatings, insulation, harness materials, structural composites, encapsulants, and flexible substrates in solar arrays having high power-to-weight ratios. However, there has been a great concern regarding the surface degradation of polymeric materials for low-Earth-orbit (LEO) application. Types of degradation include mass loss and changes of materials' mechanical, optical, and electrical properties. The sources of degradation were identified as cosmic radiation, ultraviolet radiation, meteoroids, man-made debris, contamination, vacuum, and atomic oxygen.
In particular, the reactive atmosphere, atomic oxygen which is produced by dissociation of molecular oxygen and water by ultraviolet radiation from the sun, causes a serious adverse effect on polymeric materials. Spacecraft flying with velocities of about 8 km/s at 220 km altitude experience abrasion by particulates such as micrometeroids and space debris impacts and mass loss due to chemical production of volatile oxides through reactions with the high energy atomic oxygen which has the impact energy of 5 eV (equivalent to a temperature 60,000 K.). Efforts have been undertaken by others to increase barrier properties by means of surface coatings or laminations as in the use of aluminized tape.
For further information, see D. C. Ferguson, Laboratory Degradation of Kapton in a Low Energy Oxygen Ion Beam, NASA Technical Memorandum 83530, 1983; V. Srinivasan, et al., Editors, Materials Degradation in Low Earth Orbit (LEO), particularly pages 97-105, published 1990 by The Minerals, Metals, & Materials Society, Warrendale, Pa.; A. F. Whitaker, Coatings could protect composites from hostile space environment, Advanced Materials & Processes, April, 1991; and, R. C. Tennyson, et al., Designers must account for dimensional changes in composites due to outgassing, Advanced Materials & Processes, May, 1991. It is evident from these and other studies that an important need exists for polymers having hard surfaces that are resistant to oxygen erosion.